the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 18 Sep 2024
Simulated ocean oxygenation during the interglacials MIS 5e and MIS 9e
Abstract. Recent studies investigating future warming scenarios have shown that the ocean oxygen content will continue to decrease over the coming century due to ocean warming and changes in oceanic circulation. However, significant uncertainties remain regarding the magnitude and patterns of future ocean deoxygenation. Here, we simulate ocean oxygenation with the ACCESS ESM1.5 model during two past interglacials that were warmer than the preindustrial climate, the Last Interglacial (Marine Isotope Stage (MIS) 5e, ~ 129–115 ka) and MIS 9e (~ 336–321 ka). While orbital parameters were similar during MIS 5e and MIS 9e, with lower precession, higher eccentricity and higher obliquity than pre-industrial, greenhouse gas radiative forcing was highest during MIS 9e. We find that the global ocean is overall less oxygenated in the MIS 5e and MIS 9e simulations compared to the preindustrial control run and that oxygen concentrations are more sensitive to changes in the distribution of incoming solar radiation than to differences in greenhouse gas concentrations. Large regions in the Mediterranean Sea are hypoxic in the MIS 5e simulation, and to a lesser extent in the MIS 9e simulation, due to an intensification and expansion of the African Monsoon, enhanced river run-off and resulting freshening of surface waters and stratification. Upwelling zones off the coast of North America and North Africa are weaker in both simulations compared to the preindustrial control run, leading to less primary productivity and export production. Antarctic Bottom Water is less oxygenated, while North Atlantic Deep Water and the North Pacific Ocean at intermediate depths are higher in oxygen content. All changes in oxygen concentrations are primarily caused by changes in ocean circulation and export production and secondarily by changes in temperature and solubility.
Competing interests: One of the co-authors is a co-editor-in-chief of Climate of the Past.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.-
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-2675', Anonymous Referee #1, 22 Oct 2024
The study focuses on oxygenation during past interglacial periods, showing clear results on oxygenation patterns and differences between MIS 5e and MIS 9e in terms of ocean oxygenation. I recommend that the paper be accepted for publication with minor revisions.1 When comparing the PI and global distributions of dissolved O2 concentration, did you account for the influence of greenhouse gases increase? Maybe this comparison can further elucidate the effects of greenhouse gases. Is there any simulation conducted with modern atmospheric concentrations?
2 The article does not perform a significance test when calculating anomalies, which should be included.
3 Some of the text in the figures is too small to read clearly (e.g. titles in Fig. 2,3,4..). Please increase the font size to improve readability.
4 Certain figures appear unnecessary. I suggest the authors to reduce the number of figures in appendix.
5 More discussion about how ocean oxygen may change in the context of increasing carbon dioxide concentrations in the future and the potential impacts of such changes. I hope these suggestions assist the authors in revising the manuscript.Citation: https://doi.org/10.5194/egusphere-2024-2675-RC1 -
AC1: 'Reply on RC1', Bartholomé Duboc, 21 Dec 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2675/egusphere-2024-2675-AC1-supplement.pdf
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AC1: 'Reply on RC1', Bartholomé Duboc, 21 Dec 2024
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RC2: 'Comment on egusphere-2024-2675', Anonymous Referee #2, 29 Oct 2024
The study by Duboc et al. investigated ocean oxygenation during the MIS 5e and MIS9e based on ACCESS-ESM1.5. The topic fits the CP, but the organization of the manuscript needs to improve.
Major comments:
- In the Introduction section, the authors provide reconstructed ocean oxygenation in the past climate using considerable length, and I think this paragraph can be summarized more briefly. Moreover, as this manuscript focused on the modeling, I recommend providing some key points on research progress on the numerical modeling. In addition, I suggest adding a paragraph at the end of this section by giving the organization of this manuscript.
- Lines 47-53: I feel confused about this paragraph. Why do you separate the Mediterranean Sea individually? If necessary, please provide transition sentences.
- In Section 2, the authors provide 1000~2000 model-year simulations in this study. In Figure A2, I don’t think the simulated conditions reaching quasi-equilibrium. It is obvious that the global mean O2 concentration, mean O2 concentration in the Mediterranean Sea, and AABW mean O2 still show a decreasing trend. Indeed, the deep ocean circulation generally needs more than 4000 model-year integration to reach quasi-equilibrium. I am wondering whether this imbalance may have an impact on your results.
- In Section 3.1, the authors provide oxygenation changes in AABW, NADW, NPIW, and OMZ. Why do you choose these water/regions for analysis? Any opinions on other water masses? At least, the authors should introduce the importance of these water masses at the beginning of this section.
- In Section 3.1.1, authors declare changes in AOU, export production, and remineralization rates during the MIS 5e and MIS 9e. However, readers may feel confused about how these factors influence ocean oxygenation, because not all readers are familiar with these words. I suggest adding some illustrations on the definition and impact of AOU, export production and remineralization rates.
- Following comment #4, in Section 3.1.1, the authors declare changes in dissolved oxygen concentrations in AABW are linked with changes in ocean circulations, with the increase in export production and remineralization rates. Do changes in ocean circulation impact export production and remineralization rates? If so, how do you distinguish their exact contribution to the ocean oxygen concentrations? Moreover, ocean circulation, export production, and remineralization rates are linked with increased temperature. Therefore, I speculate that changes in thermal structures in the ocean induced by solar insolation anomalies may drive variations in ocean oxygenation ultimately. Same comments on Section 3.1.2-3.1.4.
- Following comment #1, in Section 3.2, I am curious about the uniqueness of the Mediterranean Sea. I suggest adding some sentences in the Introduction and Section 3 that illustrate the necessity of separating the results of the Mediterranean Sea individually, e.g. its large region, substantial drift in oxygenation…
- Lines 246-250. How is this conclusion proposed? Indeed, although Earth’s orbit and greenhouse gases are the main external forcings in MIS 5e and MIS 9e. However, changes in incoming solar insolation are the dominant external forcings, with its radiative forcing quite larger than the greenhouse gases. I speculate that the less oxygenated conditions during MIS 5e and MIS 9e may be tied to changes in solar insolation driven by Earth’s orbit compared with the PI, rather than their differences in greenhouse gases.
- In the Abstract and Introduction sections, the authors illustrated that the MIS 5e and MIS 9e may provide a reference for ocean oxygenation in a warmer world. I want to see more discussions on how the less oxygenated conditions during MIS 5e and MIS 9e may provide insight for reducing uncertainties in future ocean deoxygenation.
Minor comments:
- Line 160, adding abbreviation (OMZ).
- Fig. 2, adding boxes indicating the region of AABW, NADW….
- Adding significant test for anomalies between MIS 5e and PI, MIS 9e and PI, and MIS 9e and MIS 5e.
- Enlarging the titles in the figures, they are too small.
Citation: https://doi.org/10.5194/egusphere-2024-2675-RC2 -
AC2: 'Reply on RC2', Bartholomé Duboc, 21 Dec 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2675/egusphere-2024-2675-AC2-supplement.pdf
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RC3: 'Comment on egusphere-2024-2675', Anonymous Referee #3, 29 Oct 2024
Please find my suggestions attached as a PDF.
-
AC3: 'Reply on RC3', Bartholomé Duboc, 21 Dec 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2675/egusphere-2024-2675-AC3-supplement.pdf
-
AC3: 'Reply on RC3', Bartholomé Duboc, 21 Dec 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-2675', Anonymous Referee #1, 22 Oct 2024
The study focuses on oxygenation during past interglacial periods, showing clear results on oxygenation patterns and differences between MIS 5e and MIS 9e in terms of ocean oxygenation. I recommend that the paper be accepted for publication with minor revisions.1 When comparing the PI and global distributions of dissolved O2 concentration, did you account for the influence of greenhouse gases increase? Maybe this comparison can further elucidate the effects of greenhouse gases. Is there any simulation conducted with modern atmospheric concentrations?
2 The article does not perform a significance test when calculating anomalies, which should be included.
3 Some of the text in the figures is too small to read clearly (e.g. titles in Fig. 2,3,4..). Please increase the font size to improve readability.
4 Certain figures appear unnecessary. I suggest the authors to reduce the number of figures in appendix.
5 More discussion about how ocean oxygen may change in the context of increasing carbon dioxide concentrations in the future and the potential impacts of such changes. I hope these suggestions assist the authors in revising the manuscript.Citation: https://doi.org/10.5194/egusphere-2024-2675-RC1 -
AC1: 'Reply on RC1', Bartholomé Duboc, 21 Dec 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2675/egusphere-2024-2675-AC1-supplement.pdf
-
AC1: 'Reply on RC1', Bartholomé Duboc, 21 Dec 2024
-
RC2: 'Comment on egusphere-2024-2675', Anonymous Referee #2, 29 Oct 2024
The study by Duboc et al. investigated ocean oxygenation during the MIS 5e and MIS9e based on ACCESS-ESM1.5. The topic fits the CP, but the organization of the manuscript needs to improve.
Major comments:
- In the Introduction section, the authors provide reconstructed ocean oxygenation in the past climate using considerable length, and I think this paragraph can be summarized more briefly. Moreover, as this manuscript focused on the modeling, I recommend providing some key points on research progress on the numerical modeling. In addition, I suggest adding a paragraph at the end of this section by giving the organization of this manuscript.
- Lines 47-53: I feel confused about this paragraph. Why do you separate the Mediterranean Sea individually? If necessary, please provide transition sentences.
- In Section 2, the authors provide 1000~2000 model-year simulations in this study. In Figure A2, I don’t think the simulated conditions reaching quasi-equilibrium. It is obvious that the global mean O2 concentration, mean O2 concentration in the Mediterranean Sea, and AABW mean O2 still show a decreasing trend. Indeed, the deep ocean circulation generally needs more than 4000 model-year integration to reach quasi-equilibrium. I am wondering whether this imbalance may have an impact on your results.
- In Section 3.1, the authors provide oxygenation changes in AABW, NADW, NPIW, and OMZ. Why do you choose these water/regions for analysis? Any opinions on other water masses? At least, the authors should introduce the importance of these water masses at the beginning of this section.
- In Section 3.1.1, authors declare changes in AOU, export production, and remineralization rates during the MIS 5e and MIS 9e. However, readers may feel confused about how these factors influence ocean oxygenation, because not all readers are familiar with these words. I suggest adding some illustrations on the definition and impact of AOU, export production and remineralization rates.
- Following comment #4, in Section 3.1.1, the authors declare changes in dissolved oxygen concentrations in AABW are linked with changes in ocean circulations, with the increase in export production and remineralization rates. Do changes in ocean circulation impact export production and remineralization rates? If so, how do you distinguish their exact contribution to the ocean oxygen concentrations? Moreover, ocean circulation, export production, and remineralization rates are linked with increased temperature. Therefore, I speculate that changes in thermal structures in the ocean induced by solar insolation anomalies may drive variations in ocean oxygenation ultimately. Same comments on Section 3.1.2-3.1.4.
- Following comment #1, in Section 3.2, I am curious about the uniqueness of the Mediterranean Sea. I suggest adding some sentences in the Introduction and Section 3 that illustrate the necessity of separating the results of the Mediterranean Sea individually, e.g. its large region, substantial drift in oxygenation…
- Lines 246-250. How is this conclusion proposed? Indeed, although Earth’s orbit and greenhouse gases are the main external forcings in MIS 5e and MIS 9e. However, changes in incoming solar insolation are the dominant external forcings, with its radiative forcing quite larger than the greenhouse gases. I speculate that the less oxygenated conditions during MIS 5e and MIS 9e may be tied to changes in solar insolation driven by Earth’s orbit compared with the PI, rather than their differences in greenhouse gases.
- In the Abstract and Introduction sections, the authors illustrated that the MIS 5e and MIS 9e may provide a reference for ocean oxygenation in a warmer world. I want to see more discussions on how the less oxygenated conditions during MIS 5e and MIS 9e may provide insight for reducing uncertainties in future ocean deoxygenation.
Minor comments:
- Line 160, adding abbreviation (OMZ).
- Fig. 2, adding boxes indicating the region of AABW, NADW….
- Adding significant test for anomalies between MIS 5e and PI, MIS 9e and PI, and MIS 9e and MIS 5e.
- Enlarging the titles in the figures, they are too small.
Citation: https://doi.org/10.5194/egusphere-2024-2675-RC2 -
AC2: 'Reply on RC2', Bartholomé Duboc, 21 Dec 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2675/egusphere-2024-2675-AC2-supplement.pdf
-
RC3: 'Comment on egusphere-2024-2675', Anonymous Referee #3, 29 Oct 2024
Please find my suggestions attached as a PDF.
-
AC3: 'Reply on RC3', Bartholomé Duboc, 21 Dec 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-2675/egusphere-2024-2675-AC3-supplement.pdf
-
AC3: 'Reply on RC3', Bartholomé Duboc, 21 Dec 2024
Peer review completion
Journal article(s) based on this preprint
Data sets
Simulated ocean oxygenation during the interglacials MIS 5e and MIS 9e Nicholas K.H. Yeung and Bartholomé Duboc https://doi.org/10.26190/unsworks/30420
Simulated ocean oxygenation during the interglacials MIS 5e and MIS 9e Nicholas K.H. Yeung and Bartholomé Duboc https://doi.org/10.26190/unsworks/30420
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Bartholomé Duboc
Katrin J. Meissner
Laurie Menviel
Nicholas K. H. Yeung
Babette Hoogakker
Tilo Ziehn
Matthew Chamberlain
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(23941 KB) - Metadata XML